Lubricating compositions



United States Patent 3,337,456 LUBRICATING COMPOSITIONS Andreas G. Papayannopoulos, Woodbury, N.J., assignor to Mobil Oil Corporation, a corporation of New York No Drawing. Filed Sept. 8, 1965, Ser. No. 485,912 16 Claims. (Cl. 252-32.5)

This invention relates to lubricating compositions having extreme pressure properties and in particular it relates to lubricating oil compositions containing novel metal complexes of oil-insoluble phosphorus compounds.

Extreme pressure lubricants are extensively used in lubricating engines and transmissions of trucks, tractors or other automotive vehicles One of the requirements of extreme pressure lubricants is that they possess the ability to form a film on the surfaces of the moving metal parts. Ordinarily, when the lubricant is applied to the metal surfaces of the engine or transmission, the high pressures present in the operation of such equipment often cause the lubricant film to become disrupted. As a result metal makes contact with metal occasioning seizure and welding to occur. The formation of a tough film of lubricant on the metal surfaces prevents this seizure and welding from occurring.

One means of forming this lubricant film on the metal is achieved by chemical reaction. The additives, blended into the lubricating oil compositions, are able to react with the metal at the surface. The resulting metal reaction product is.in the form of a thin film which coats the metal surfaces. The most commonly used additives include oil-soluble compounds containing sulfur, chlorine and phosphorus atoms, bonded in a particular chemical state, with which the metal may react to form sulfides, phosphates and chlorides. Unfortunately, however, the resulting film is usually only momentary. The film is either loosely held to the metal surface and is wiped away or squeezed away by the move ment of the metal parts, or else the presence of the particular anionic-reacting radical -is insuflicient to form strong bonds with the metal. Quite often, the metal reaction product is as soluble in the oil as the additive and hence it is dissolved away from the metal surface into the oil composition. To overcome the short-lived effectiveness of these additives, higher concentrations of additives must be employed so that the disrupted film may be continually replaced by a new film.

In the past, phosphorus and sulfur compounds, such as organic phosphates, phosphosulfurized hydrocarbons, sulfur-treated fats and olefins, dithiophosphate and sulfides have been used as extreme pressure additives. The hydrocarbon group, however, must be of sufficient size to render the additive oil-soluble; thus the amount of sulfur and phosphorus atoms in the compound is diluted. On the other hand, lower hydrocarbon compounds are too insoluble in oil to provide uniform extreme pressure properties.

More recently, it has also been the practice to employ a plurality of additives for extreme pressure purposes wherein each additive separately contributes a metal-reactive component to the oil. However such practices have not successfully avoided the problems hitherto faced. A single oil-soluble additive capable of forming a tough long-lasting film on metal surfaces would therefore be advantageous for the sake of economy and performance.

It is a major object of this invention to provide improved extreme pressure lubricant compositions.

Another object of this invention is to provide lubricants containing oil-soluble extreme pressure agents which will form strong protective coatings over metal.

A further object of this invention is to provide an oilsoluble additive for lubricating oils which are adapted to form oil insoluble coatings for metals.

3,337,456 Patented Aug. 22, 1967 Another object of this invention is to provide novel oil-soluble complexes containing chlorine and trivalent phosphorus atoms.

A further object of this invention is to provide extreme pressure lubricating compositions having improved storage stability.

Another object of this invention is to provide a method of preparing extreme pressure agents for lubricating oils having sufficient solubility in oil to provide extreme pressure properties.

These and other objects of this invention will become apparent from the following description.

It has now been discovered that lubricating oil compositions having excellent extreme pressure properties may now be prepared by adding to a major proportion of a lubricating oil a minor proportion sufiicient to provide extreme pressure properties thereto of a complex of (1) a chloroalkylphosphite, and (2) a basic alkaline earth metal petroleum or aromatic sulfonate or basic alkaline earth metal phenate. Preferably the alkyl radical of the phosphite contains from 1 to 4 carbon atoms, although the maximum may be as high as 20 carbon atoms.

The lubricating compositions of this invention are particularly suitable in lubricating transmission, final drive, hydraulic systems and even the engines of vehicles equipped with high pressure motors, such as industrial or Iagricultural tractors, and as automatic transmission fluids or transaxle fluids. Although the phosphite is itself insoluble in oil, it is discovered that the'complexing of the phosphite with the basic metal sulfonate or phenate renders the resulting complex product sufiiciently oilsoluble to enable the oil medium to carry the product homogenously throughout the machinery. I have theorized that the conditions in such low-speed-high-torque operations as found in tractor motor or transmission operations appear to break the bonds which form the soluble complex and, at the same time, permit the reaction between the metal used in the construction of the tractor and the chloroalkylphosphite. This newly-formed metal phosphite provides a film that is tenacious enough to withstand the pressures of the machine and to resist removal by the oil owing to its insolubility therein. Furthermore, the residual basic metal salt which is dissolved in the oil can act as a neutralizing agent or detergent for the oil. In other words, as theorized in this invention, the mechanism of the formation of the protective film is brought about by an almost simultaneously breaking down of the oil-soluble complex and metal reaction with the chloroalkylphosphite. The resulting metal phosphite film is not removed even after many hours of machinery operation.

While phophorus compounds generally possess extreme pressure properties, the lower alkylphosphite compounds are alone so insoluble in oil that they cannot be,used elfectively or economically. In fact, the addition of a chloro-lower-alkylphosphite and the basic alkaline earth metal sulfonate or phenate' to oil as individual additives does not produce the same results as those obtained from the novel complex additives of this invention. The phosphites separate out of the oil during storage even at temperatures at which the complex is reacted indicating that in situ reactions do not occur. The two compounds must be therefore reacted prior to the addition to the lubricating oil in order to obtain all of the advantages from the extreme pressure properties of the phosphites.

The complexes of this invention are prepared by mixing the reactants together and heating at a temperature in the range of about to about 200 F. The reactants may be combined in any convenient manner and the reaction mass is stirred until a homogenous solution is obtained. The time for the reaction usually lasts from about 5 to about 30 minutes. When the resulting clear liquid product is added to an oil at any desired concentration, the resulting oil solution remains stable for a considerable length of time, even at elevated temperatures.

The chloroalkylphosphite reactant suitable for use in this invention includes the mono-, bisand tris-chloroalkylphosphites. These compounds may be prepared by known commercial methods, such as the reaction between phosphorus trichloride and alcohols or alkylene oxides. The total number of carbon atoms in the alkyl group may range from 1 to about 20. It is preferred to use the relatively insoluble phosphite in this invention, and phosphites having from 1 to 4 carbon atoms are employed with maximum benefit. The most preferred reactant is tris-betachloroethylphosphite. Other phosphites include those having mixed alkyl groups such as methyl-ethyl, methyl-propyl, methyl-isopropyl and the like. Many commercial chloroalkylphosphites contain mixtures of alkyl groups. Although their oil solubility may be very low low they have been useful in forming the complexes of this invention. It is believed of special advantage that the chlorine atom be attached in the alpha or, more preferably, beta position of the alkyl radical in order that the concurrent breakdown of the complex and film forming reaction be achieved to the most desirable eifect. Thus the most preferred position for the chlorine atom on alkyl groups having 2 or more carbon atoms is the beta position.

The basic alkaline earth metal sulfonates and phenates which may be used in this invention include those in which excess metal has been combined with the normal metal salts thereof. These compounds are referred to as overbased metal sulfionates and phenates. The higher the degree of overbasing the less is necessary to form the oil soluble complex. The metal used in these overbased salts are taken from Group II of the Periodic Table: barium, calcium, and magnesium are especially effective. Those overbased sulfonate salts described in U.S. Patents Nos. 3,133,019 and 3,158,572 are representative of the suitable sulfonate reactants for use in this invention. They include the petroleum and aromatic sulfonates. The alkaline earth metal phenates described in US. Patent No. 2,916,454 are examples of the phenate reactants suitable for use in this invention.

The amount of metal in the overbased salts may range from about 1% to about 20% of the total compound. These basic compounds are also rated for alkalinity by a total base number (TBN) in terms of milligrams of potassium hydroxide per gram of sample, using the ASTM D-664 method. Suitable basic salts having TBNs ranging from about to 400 may be used.

In forming the complex of this invention it is desirable to have a minimum Weight ratio of 1:1 of the overbased timum benefit that the complex contain at least of the metal salt. The amount of complex added to the lubricating oil may range from 0.001% to about 20% by weight of the total lubricant; from about 0.1% to about 3 by Weight is normally sufficient.

The following examples are given to further describe the invention without imparting any limitation thereto; mention of parts or percent not otherwise designated are deemed to be on a weight basis.

EXAMPLE I To a reactor equipped with a stirrer and thermometer were added 50 grams of tris-betachloroethylphosphite and grams of an overbased calcium petroleum sulfonate, having 10% calcium with a TBN of 300. The mixture was stirred at F. until homogenous. The resulting product was a clear liquid.

EXAMPLE II Using the procedure of Example I, 50 grams of trisbetachloroethylphosphite was stirred together with 200 grams of an overbased calcium petroleum sulfonate having 2.8% calcium and a TBN of 38. The resulting product was a clear liquid.

EXAMPLE III Using the procedure of Example I, 20 grams of trisbetachloroethylphosphite was stirred together with 80 grams of an overbased calcium sulfona-te having 7.28% calcium and a TBN of 203. The reaction temperature in this example was F. The resulting product was a clear liquid.

Evaluation of product The products of the above examples are all soluble in oil, and when tested by the known extreme pressure tests they register an extremely high torque rating. Moreover, the surface of the metal in wear tests remain smooth.

The product of Example 1a was tested in the Falex load test, the Almen load test and the SAE tests. These tests have been described thoroughly in literature. Three percent of the Example I complex was added to a highly refined white mineral base oil. A second complex, using the same calcium petroleum sulfonate as in Example I except that the rate of sulfonate to phosphite was 2:06, was also tested at a concentration of 2.6%. These complexes were compared with varying amounts of tricresylphos-phate, tributylphosphite and with tris-betachloroisopropylphosphite in the presence of the same calcium sulfonate. The concentrations and the results of the extreme pressure tests are tabulated in the following table. (The percent of phosphorus provided by each of the additives is also given.)

TABLE I Additive (wt. percent):

Calcium sullonateftphosphite:

Calcium slii'riit'lij Tricresylphosph ate T ributylphosphite Tris-betachloroisopropylphosphite Phosphorus Tests (1b.):

Falex Load Test:

Pass 1 Surface Distress.

Gone. in Oil Pass Pass Fail Fail Pass Fail None None Seizure Ridging, Trace- Seizure Rippling None metal salt to the chloroalkylphosphite. This ratio may be as high as deemed necessary, although a range of 1 to 5:1

It may be seen from these tests that the complexes of this invention (items a and b above) provide excellent is normally satisfactory. It is important therefore for op- Z5 extreme pressure protection. Known extreme pressure additives and uncomplexed alkylphosphites, even at higher concentrations, are less effective. The load at failure is much lower than those obtained with the complex and the surface of the metal in the test shows signs of seizure or other surface abrasion. For example, in the case of the tributylphosphite the surface had ridges and ripples.

The complex product of Example I was tested for storage stability over an extended period at both room temperature and at 150 F. As a comparison, the reactants used to prepare the product of Example I were added individually to another sample of the base oil using the same concentration for each as would be present in the complex. The base oil in this test was a mixture of mineral oil stock. After one week at room temperature the complex product remained dissolved in oil in a clear solution. The sample containing the individual components showed a precipitate. Of the samples held for one week at 150 F., the product of Example I remained in solution in the oil; a considerably greater precipitate formed in the comparison blend than the corresponding room temperature sample. This test indicates that the complex cannot be produced in the oil medium.

It has further been found that suitable complexes can not be prepared from neutral sulfonates or phenates. The salt must contain some degree of overbasing. Using the 2:1 weight ratio of the sulfonate or phenate to the phosphite as in Example I, complexes were prepared from both overbased and neutral salts. The complexes were tested in the storage stability test at a concentration of 3%. The same base stock was used as in the previous test. The neutral sulfonate reactants were barium dinonyl naphthalene sulfonate, ethylenediamine dinonyl naphthalene sulfonate, lead dinonyl naphthalene sulfonate, sodium petroleum sulfonate and zinc petroleum sulfonate. The overbased sulfonate reactants were also a calcium petroleum sulfonate containing 3% calcium with a TBN of 22; a synthesized barium sulfonate containing 15% barium with a TBN of 63; a synthesized magnesium sulfonate containing 7.2% magnesium with a TBN of 300; and a calcium phenate containing 9.3% calcium with a TBN of 255. The results of the solubility in oil and the storage stability of the complex are tabulated below.

The above test results indicate that the complexes of this invention are both novel and extremely useful in providing extreme pressure properties to a lubricating oil. The soluble complexes are stable in oil for long periods of time and at normal storage temperatures.

Lubricant mineral oils may be used for the base fluid in this invention, as well as synthetic ester lubricants and polymer lubricants. The complexes of this invention are compatible with other known additives for lubricating oils and they may be combined with other detergents, viscosity index improvers, antioxidants, antifoamers, and the like. Of incidental utility in this invention is the detergency nature of the sulfonates and phenates. The detergency and neutralizing power of the complexes remains at a high level even before the breakdown. After the breakdown of the phosphite complex, these overbased salts are available to continue to provide equivalent detergency and neutralizing properties to the oil composition.

Although the present invention has been described hereinabove by means of specific illustrative embodiments, it is not intended that the scope thereof be limited in any way except as indicated in the following claims.

I claim:

1. A novel complex reaction product prepared by the reaction at up to about 200 F. of a chloroalkylphosphite wherein the alkyl group has from 1 to about 20 carbon atoms and an overbased metal salt selected from the group consisting of alkaline earth metal sulfonates and phenates.

2. A novel complex reaction product prepared by the reaction at up to about 200 F. of a betachloroalkylphosphite wherein the alkyl group has from 1 to about 20 carbon atoms and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates.

3. A novel complex reaction product prepared by the reaction at from about to about 200 F. of trisbetachloroalkylphosphite wherein the alkyl group has from 1 to 4 carbon atoms and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the weight ratio of metal salt to phosphite is at least about 1:1.

4. A novel complex reaction product prepared by the reaction at from about 100 to about 200 F. of trisbetachloroethylphosphite and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the percent of metal is in the range of about 1.0% to about 20% wherein the weight ratio of metal salt to phosphite is at least about 1:1.

5. The reaction product of claim 4 wherein the weight ratio of metal salt to phosphite is in the range of about 1:1 to 5:1.

6. The method of producing novel oil-soluble reaction products comprising the steps of (1) admixing a chloroalkylphosphite wherein the alkyl groups contain from 1 to about 20 carbon atoms and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the weight ratio of metal salt to phosphite is at least about 1:1 and (.2) stirring the resulting reaction mixture while maintaining the temperature in the range of about 100 F. to about 200 F. until a homogenous solution is obtained.

7. A method of producing novel oil-soluble reaction products comprising the steps of (1) admixing a betachloroalkylphosphite wherein the alkyl groups contain from 1 to 4 carbon atoms and an overbased alkaline earth metal salt selected from the group consisting of sulfonate and phenates wherein the weight ratio of metal salt to phosphite is at least about 1:1 and (2) stirring the resulting reaction mixture in the temperature in the range of about 100 F. to about 200 F. until a homogeneous solution is obtained.

8. The method of claim 7 wherein the betachloroalkylphosphite is tris-betachloroethylphosphite.

9. The method of claim 7 wherein the metal content of the overbased metal salt is in the range of about 1% to about 20%.

I 10. The method of claim 7 wherein the overbased metal salt is an overbased calcium sulfonate.

11. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion sufficient to provide extreme pressure properties thereto of an oil-soluble reaction product prepared by the heating at up to about 200 F., a mixture of a chloroalkylphosphite wherein the alkyl group has from 1 to about 20 carbon atoms and a basic alkaline earth metal salt selected from the group consisting of an alkaline earth metal sulfonate and an alkaline earth metal phenate wherein the weight ratio of metal salt to phosphite is at least about 1:1.

12. A lubricating oil composition containing a major proportion of a lubricating oil and a minor proportion sufficient to provide extreme pressure properties thereto of an oil-soluble reaction product prepared by the reaction at from about 100 to about 200 F. of a betachloroalkylphosphite, wherein the alkyl group has from 1 to 4 carbon atoms, and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the weight ratio of metal salt to phosphite is at least about 1:1.

13. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion sufiicient to provide extreme pressure properties thereto of an oil-soluble reaction product prepared by the reaction at from about 100 to about 200 F. of trisbetachloroalkylphosphite wherein the alkyl group has from 1 to 4 carbon atoms and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the weight ratio of metal salt to phosphite is at least about 1:1.

14. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion sufiicient to provide extreme pressure properties thereto of an oil-soluble reaction product prepared by the reaction at from about 100 to about 200 F. of trisbetachloroethylphosphite and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the percent of metal is in the range 8 of about 1% to about 20% wherein the weight ratio of metal salt to phosphite is at least about 1:1.

15. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion suificient to provide extreme pressure properties thereto of an oilsoluble reaction product prepared by the reaction at from about 100 to about 200 F. of a trisbetachloroethylphosphite and an overbased alkaline earth metal salt selected from the group consisting of sulfonates and phenates wherein the Weight ratio of metal salt to phosphite is in the range of about 1:1 to about 5:1.

16. A lubricating oil composition comprising a major nate wherein the weight ratio of sulfonate to phosphite is in the range of about 1:1 to 5:1.

References Cited UNITED STATES PATENTS 12/1959 Bradley et al. 25242.7 4/1962 Elliott et al. 25233.4 X

DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

11. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND A MINOR PROPORTION SUFFICIENT TO PROVIDE EXTREME PRESSURE PROPERTIES THERETO OF AN OIL-SOLUBLE REACTION PRODUCT PREPARED BY THE HEATING AT UP TO ABOUT 200*F., A MIXTURE OF A CHLOROALKYLPHOSPHITE WHEREIN THE ALKYL GROUP HAS FROM 1 TO ABOUT 20 CARBON ATOMS AND A BASIC ALKALINE EARTH METAL SALT SELECTED FROM THE GROUP CONSISTING OF AN ALKALINE EARTH METAL SULFONATE AND AN ALKALINE EARTH METAL PHENATE WHEREIN THE WEIGHT RATIO OF METAL SALT TO PHOSPHITE IS AT LEAST ABOUT 1:1. 